Green’s Dictionary of Slang

headache n.

1. [1920s+] (orig. US) a problem, a cause of anxiety, a worry.

2. [1930s] (US) one’s husband or wife, boyfriend or girlfriend.

3. a problematic individual.

In compounds

headache-man (n.)

[1940s–50s] (US drugs) a Federal narcotics agent.

headache-stick (n.)

[late 19C+] (US black) a stick used as a club, a police baton or truncheon.